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The call log of a seized iPhone, with numbers redacted.

You may think of your iPhone as a friendly personal assistant. But once it's alone in a room full of law enforcement officials, you might be surprised at the revealing things it will say about you.

On Tuesday the American Civil Liberties Union published a report it obtained from a drug investigation by the Immigration and Customs Enforcement (ICE) agency, documenting the seizure and search of a suspect's iPhone from her bedroom. While it's no surprise that a phone carries plenty of secrets, the document presents in stark detail a list of that personal information, including call logs, photos, videos, text messages, Web history, eight different passwords for various services, and perhaps most importantly, 659 previous locations of the phone invisibly gathered from Wifi networks and cell towers.

"We know the police have started using tools that can do this. We’ve known the iPhone retains records of the cell towers it contacts. But we’ve never before seen the huge amount of data police can obtain," says ACLU technology lead Chris Soghoian, who found the report in a court filing. "It shouldn’t be shocking. But it’s one thing to know that they’re using it. It’s another to see exactly what they get."

The phone search and seizure described in the documented case required a warrant. But the legality of warrantless phone searches remains an open issue. At U.S. borders or when arresting a suspect, for instance, police and government officials have argued that no such warrant is required.